Granite

Coarse-grained, gray, and speckled with a granular texture; typically Mohs 6–7, vitreous-to-dull luster, interlocking crystals, and poor cleavage as a whole (feldspar has cleavage). Specific gravity is about 2.63–2.75.

An intrusive igneous rock formed when silica-rich magma cooled slowly deep underground, allowing large crystals to grow. Most granite formed during Precambrian to Phanerozoic continental crustal events.

Widely used for countertops, monuments, flooring, building stone, and crushed aggregate; attractive polished pieces are also collected.

The visible gray-white grains commonly include quartz and potassium/plagioclase feldspar, with dark biotite or amphibole. Its coarse texture indicates slow underground cooling rather than volcanic eruption.

Identify it by its visible interlocking grains, hard surface, light gray color, and lack of layering or foliation; it commonly occurs in continental mountain belts and exposed plutons. A small ordinary fragment is usually worth $1–$10; polished or unusual specimens may sell for $10–$50.